The pyrolysis of organic matter such as biomass, wood or sugars, is a known reaction useful for obtaining compositions of bio-oils or low molecular weight carbonyl compounds. The compositions of bio-oils or low molecular weight carbonyl compounds may be referred to as pyrolysis product compositions.
Pyrolysis product compositions, obtained by the pyrolysis of sugars, have been shown to be a useful source of glycolaldehyde. Glycolaldehyde, also known as hydroxyactealdehyde, is the primary low molecular weight carbonyl compound present in the pyrolysis product composition obtained through the pyrolysis of glucose according to U.S. Pat. No. 7,094,932. Additional low molecular weight carbonyl compounds present in the pyrolysis product composition prepared by the pyrolysis of glucose may be: formaldehyde; glyoxal; acetol and pyruvaldehyde.
The pyrolysis product composition of sugars may be used commercially as an aqueous solution in the food industry for use in the browning of foodstuffs, wherein glycolaldehyde is considered to play a significant role as an active ingredient. U.S. Pat. No. 7,094,932 discloses exemplary pyrolysis product compositions obtained by the pyrolysis of sugars suitable for human consumption.
The pyrolysis product composition may be purified to obtain glycolaldehyde. U.S. Pat. No. 5,292,541, discloses an exemplary purification process comprising multiple distillation steps followed by a solvent-induced precipitation to obtain glycolaldehyde. U.S. Pat. No. 7,094,932 discloses the removal of formaldehyde from a pyrolysis product composition by utilizing analytical HPLC.
It is known that pure glycolaldehyde may be used as an intermediate for the preparation of chemicals such as ethylene glycol. U.S. Pat. Nos. 4,200,765 , 4,321,414, 4,317,946 and 4,496,781 disclose examples of hydrogenation of pure glycolaldehyde, in particular when pure glycolaldehyde is hydrogenated employing a homogenous ruthenium catalyst.
U.S. Pat. No. 4,496,781 identifies a variety of difficulties encountered when hydrogenating glycolaldehyde in the presence of formaldehyde and indicates that time-consuming separation procedures are required and a reduction in yield of the desired product is observed. U.S. Pat. No. 5,210,337 also highlights that the presence of even a minute amount of formaldehyde, as low as 0.1 wt %, can often poison a hydrogenation catalyst and consequently hinder transformations such as hydrogenation of glycolaldehyde.
In order to overcome the difficulties presented by the presence of formaldehyde in reaction mixtures, extensive investigation of hydrogenation catalysts that are unaffected by the presence of formaldehyde have been undertaken. U.S. Pat. No. 5,210,337 discloses rhenium catalysts resistant to formaldehyde poisoning.
Therefore, there is a need for a process for reducing the weight percentage of formaldehyde present in a pyrolysis product composition comprising low molecular weight carbonyl compounds wherein the process used is high yielding (i.e. a high percentage recovery of the low molecular weight carbonyl compounds), industrially and commercially feasible, and the composition is suitable for use for subsequent chemical transformations.